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We read with interest the elegant study by Avidan et al.1 investigating the effect of different activators on the thromboelastogram in the absence and presence of aprotinin. Although they suggest that kaolin use with the thromboelastogram has not been reported, we recently presented data in abstract form from an ongoing in vivo
study. 2

In 12 patients undergoing cardiopulmonary bypass and receiving low-dose aprotinin (1 million-KIU loading dose), we found no differences between
the celite- or kaolin-activated R time, K time, angle, or maximum amplitude either prior to or after the aprotinin loading dose (table 1). Our preliminary results do not support the authors’ findings of a shorter R time and greater angle and maximum amplitude in kaolin-activated parameters in the absence
of aprotinin.

Table 1. Celite- and Kaolin-activated Thrombelastogram Parameters before and after Aprotinin Loading Dose

In the presence
of aprotinin, there was a tendency toward similar prolongation of the R and K times (40%) and decreases in the angle (10%) in both celite and kaolin samples compared to baseline (table 1), although this interim analysis was not adequately powered to confirm statistical significance. Until completion of our study in patients receiving both high- and low-dose aprotinin, we echo the caution of Avidan et al.
that changes in the celite- or kaolin-activated thromboelastogram R time may occur in the presence of aprotinin.